Flagstaff
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flagstaff clear sky chart from 2005-11-05 to 2018-02-22.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
55%
16215
34%
48882
22%
16174
67%
16174
45%
24031

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
47%
780
32%
2522
22%
776
62%
776
37%
1269
January16th to endNight
46%
832
35%
2704
23%
832
63%
832
37%
1372
February1st to 15thNight
50%
760
32%
2414
23%
760
65%
760
43%
1172
February16th to endNight
40%
660
36%
1973
24%
660
57%
660
37%
1028
March1st to 15thNight
45%
720
36%
1980
20%
720
61%
720
45%
1010
March16th to endNight
48%
768
34%
2112
17%
768
63%
768
47%
1064
April1st to 15thNight
36%
686
29%
1945
12%
686
51%
686
39%
988
April16th to endNight
42%
540
41%
1677
19%
540
64%
540
46%
730
May1st to 15thNight
47%
540
35%
1619
20%
539
60%
539
52%
719
May16th to endNight
46%
561
34%
1684
19%
561
59%
561
47%
755
June1st to 15thNight
50%
540
32%
1620
22%
540
59%
540
59%
694
June16th to endNight
68%
540
34%
1620
27%
540
73%
540
65%
674
July1st to 15thNight
73%
510
19%
1530
15%
510
75%
510
41%
824
July16th to endNight
74%
564
17%
1593
15%
531
74%
531
32%
956
August1st to 15thNight
79%
539
26%
1611
21%
536
80%
536
40%
855
August16th to endNight
80%
599
33%
1814
29%
599
82%
599
43%
957
September1st to 15thNight
74%
720
28%
1980
21%
720
79%
720
45%
1099
September16th to endNight
69%
716
45%
1980
27%
716
81%
716
64%
888
October1st to 15thNight
57%
720
37%
2079
21%
720
71%
720
56%
956
October16th to endNight
61%
768
43%
2304
30%
768
74%
768
54%
1051
November1st to 15thNight
54%
760
35%
2347
23%
760
68%
760
48%
1099
November16th to endNight
52%
780
40%
2535
29%
780
69%
780
47%
1130
December1st to 15thNight
51%
780
33%
2535
23%
780
66%
780
39%
1244
December16th to endNight
46%
832
32%
2704
24%
832
59%
832
32%
1497

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
342442445%6%58%
49373
Night
221332335%6%64%
49078
TransparencyDay
25%46%19%27%16%
49068
Night
20%37%20%29%18%
48884
SeeingDay
8%20%28%27%12%3
5909
Night
413%21%30%23%6%
16221

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
1324423346%63%
1746
16th to endDay
35%24423346%59%
1872
February1st to 15thDay
16%3441225%7%59%
1778
16th to endDay
143342446%7%57%
1647
March1st to 15thDay
14232235%5%7%60%
1980
16th to endDay
2413313349%61%
2112
April1st to 15thDay
1214434348%60%
2003
16th to endDay
25%23312336%65%
2280
May1st to 15thDay
2423422445%63%
2331
16th to endDay
3223323345%63%
2429
June1st to 15thDay
212212245%75%
2340
16th to endDay
221222333471%
2340
July1st to 15thDay
5%5%247%5%7%7%7%8%39%
2340
16th to endDay
7%6%38%8%47%9%8%9%25%
2467
August1st to 15thDay
8%5%25%7%5%6%6%7%7%37%
2340
16th to endDay
5%415%6%46%7%7%7%41%
2384
September1st to 15thDay
4425%5%46%7%6%7%44%
1980
16th to endDay
2212322236%68%
1980
October1st to 15thDay
331331323369%
1881
16th to endDay
2112212346%70%
1920
November1st to 15thDay
12221335%6%69%
1841
16th to endDay
3313211225%71%
1755
December1st to 15thDay
25%1432225%7%60%
1755
16th to endDay
25%345%3445%7%52%
1872
January1st to 15thNight
131432345%6%61%
2522
16th to endNight
342432344462%
2704
February1st to 15thNight
42332335%6%64%
2403
16th to endNight
131342445%7%61%
1973
March1st to 15thNight
1323213447%65%
1980
16th to endNight
1312213347%66%
2112
April1st to 15thNight
1323213447%65%
1945
16th to endNight
11212246%74%
1677
May1st to 15thNight
1112213346%71%
1619
16th to endNight
1212212235%73%
1684
June1st to 15thNight
2112112235%77%
1620
16th to endNight
1221223477%
1620
July1st to 15thNight
32145%35%5%6%8%53%
1620
16th to endNight
43245%47%8%9%12%38%
1701
August1st to 15thNight
333325%6%7%11%51%
1620
16th to endNight
21134245%7%9%54%
1814
September1st to 15thNight
32144245%7%8%55%
1980
16th to endNight
111112245%78%
1980
October1st to 15thNight
211212245%73%
2079
16th to endNight
1212212235%73%
2304
November1st to 15thNight
121232345%6%67%
2347
16th to endNight
221321233471%
2535
December1st to 15thNight
1324213448%63%
2535
16th to endNight
1436%425%46%6%54%
2704

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
21%36%24%33%9%
1747
16th to endDay
26%37%20%31%11%
1872
February1st to 15thDay
26%37%25%21%15%
1778
16th to endDay
28%36%22%28%10%
1647
March1st to 15thDay
22%4422%33%12%
1980
16th to endDay
21%46%26%28%12%
2112
April1st to 15thDay
22%35%22%32%13%
2003
16th to endDay
22%3319%35%15%
2280
May1st to 15thDay
23%3419%35%15%
2331
16th to endDay
22%3416%37%14%
2432
June1st to 15thDay
12%3211%30%39%
2340
16th to endDay
15%318%27%42%
2340
July1st to 15thDay
36%6%11%13%12%18%
2201
16th to endDay
45%10%16%14%11%1
2312
August1st to 15thDay
41%6%9%14%17%10%
2325
16th to endDay
35%7%9%19%20%7%
2384
September1st to 15thDay
34%7%9%15%17%15%
1980
16th to endDay
17%4217%34%22%
1980
October1st to 15thDay
20%3217%30%25%
1881
16th to endDay
16%2418%38%19%
1920
November1st to 15thDay
16%25%25%31%17%
1841
16th to endDay
17%2421%34%19%
1755
December1st to 15thDay
24%39%25%24%12%
1755
16th to endDay
33%38%23%23%7%
1872
January1st to 15thNight
23%4424%31%10%
2522
16th to endNight
25%35%19%32%13%
2704
February1st to 15thNight
21%36%24%27%17%
2414
16th to endNight
24%36%22%29%13%
1973
March1st to 15thNight
19%3423%36%12%
1980
16th to endNight
17%48%25%31%12%
2112
April1st to 15thNight
20%25%21%35%13%
1945
16th to endNight
13%3422%36%20%
1677
May1st to 15thNight
13%36%25%31%19%
1620
16th to endNight
14%3418%40%17%
1685
June1st to 15thNight
12%1110%30%42%
1620
16th to endNight
10%226%25%52%
1620
July1st to 15thNight
24%6%15%14%17%21%
1530
16th to endNight
31%8%22%19%13%4
1593
August1st to 15thNight
24%6%13%20%22%12%
1611
16th to endNight
22%6%12%23%25%9%
1814
September1st to 15thNight
23%5%11%20%22%15%
1980
16th to endNight
9%3217%36%29%
1980
October1st to 15thNight
14%25%21%29%27%
2079
16th to endNight
15%2416%37%24%
2304
November1st to 15thNight
18%36%23%31%17%
2347
16th to endNight
16%25%19%33%22%
2535
December1st to 15thNight
21%47%25%24%16%
2535
16th to endNight
31%37%23%24%9%
2704

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
7%24%26%26%12%2
135
16th to endDay
425%25%27%14%2
144
February1st to 15thDay
9%24%24%25%14%2
203
16th to endDay
16%34%28%15%3
264
March1st to 15thDay
8%27%34%18%8%1
270
16th to endDay
10%26%36%18%5%2
288
April1st to 15thDay
11%33%31%11%9%1
269
16th to endDay
8%42%26%15%41
270
May1st to 15thDay
9%31%34%16%6%1
288
16th to endDay
7%29%30%24%6%1
330
June1st to 15thDay
323%36%23%9%3
315
16th to endDay
39%35%36%13%1
315
July1st to 15thDay
6%8%26%42%13%2
305
16th to endDay
12%414%39%21%7%
327
August1st to 15thDay
9%318%40%20%7%
315
16th to endDay
7%321%37%21%8%
332
September1st to 15thDay
8%8%28%33%16%4
315
16th to endDay
6%17%27%29%13%5%
315
October1st to 15thDay
430%26%24%10%3
216
16th to endDay
7%12%30%22%19%7%
144
November1st to 15thDay
418%30%29%12%4
135
16th to endDay
8%22%23%25%13%5%
135
December1st to 15thDay
220%33%25%14%2
135
16th to endDay
10%19%25%29%10%4
144
January1st to 15thNight
7%14%24%27%17%8%
780
16th to endNight
7%17%24%27%17%5%
832
February1st to 15thNight
416%25%31%18%4
764
16th to endNight
6%22%28%26%13%2
660
March1st to 15thNight
5%19%26%28%15%4
720
16th to endNight
417%26%32%16%2
768
April1st to 15thNight
5%24%27%27%11%2
686
16th to endNight
223%28%28%13%3
540
May1st to 15thNight
217%30%34%13%1
540
16th to endNight
417%26%27%20%3
563
June1st to 15thNight
211%33%33%18%2
540
16th to endNight
1421%41%27%2
540
July1st to 15thNight
5%10%36%40%5%
510
16th to endNight
415%34%44%9%
564
August1st to 15thNight
415%28%48%10%
539
16th to endNight
31431%44%14%
599
September1st to 15thNight
339%26%45%10%
720
16th to endNight
39%14%26%35%10%
716
October1st to 15thNight
310%25%32%21%6%
720
16th to endNight
29%19%30%26%10%
768
November1st to 15thNight
313%25%31%21%5%
760
16th to endNight
415%23%27%19%8%
780
December1st to 15thNight
6%15%22%29%22%3
780
16th to endNight
7%15%25%30%16%4
832
Page generated at 2018-02-23 09:21:31. Version ac04

Copyright 2018 A. Danko


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